Random selection system for a slide projector

ABSTRACT

The random selection system consists of an attachment unit which is detachably mounted on the housing of the slide projector, a remote control unit which is separate and remote from the slide projector, and an extension cable connecting these units. The attachment unit contains a commutator. The remote control unit includes receiving means in the form of DC motor parts. The commutator acts as a transmitter and the motor parts as a receiver for stepping or rotating the rotor in synchronization with rotation of the movable component of the commutator. The rotor drives a seeking contact for movement in an arcuate path.

United States Patent Bennett [54] RANDOM SELECTION SYSTEM FOR A SLIDEPROJECTOR 72 inventor: Frank P. Bennett, Northbrook, 111.

[73] Assignee: GAF Corporation, New York, NY.

[22] Filed: June 24, 1968 [21] Appl. No.2 739,353

[52] u.s.c1. ..3s3/2s,31s/67s,318/685, 353/103 [511 1111.01. .0031 23/06[58] FieldoiSearch ..3s3/2s,1o3,1o4,107,10s, 353/111, 112, 114, 115,116, 117, 118-, 318/42, 43, 20.810, 20.860, 675

[56] References Clted UNITED STATES PATENTS 1,292,768 1/1919 Harle..318/43X Feb. 22, 1972 3,296,727 1/1967 Liguori ..353/117 X PrimaryExaminer-Leonard Forman Assistant Examiner-Steven L. StephanAttorney-McDouga1l, Hersh & Scot ABSTRACT The random selection systemconsists of an attachment unit which is detachably mounted on thehousing of the slide projector, a remote control unit which is separateand remote from the slide projector, and an extension cable connectingthese units. The attachment unit contains a commutator. The remotecontrol unit includes receiving means in the form of DC motor parts. Thecommutator acts as a transmitter and the motor parts as a receiver forstepping or rotating the rotor in synchronization with rotation of themovable component of the commutator. The rotor drives a seeking contactfor movement in an arcuate path.

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PATENTEDFEB22 I972 SHEET 11 HF 11 A INVENTOR FRANK F? BENNET RANDOMSELECTION SYSTEM FOR A SLIDE PROJECTOR OBJECTS OF THE INVENTION Aprimary object of the present invention is the provision of a new andimproved random selection system for a slide projector, wherein suchsystem is of simplified and low-cost construction.

Another primary object of the present invention is the provision of arandom selection system for a slide projector, which system utilizestransmitting and receiving means which in a preferred form consist of aDC stepping motor with a remote commutator.

Another object of the present invention is the provision of a randomselection system of the type described, which system has a so-calledshort-way home" feature, i.e., in the case of a circular slide tray forexample, the tray is rotated automatically in a direction resulting inthe minimum amount of rotational movement in presenting the selectedslide adjacent the slide projection gate of the projector.

Still another object of the present invention is the provision of arandom selection system of the type described, which system includessimplified selector means adapting the system for alternatelyaccommodating two types of slide trays, these trays differing in thenumber of slide-receiving spaces they contain.

Another object of the present invention is the provision of a randomselection system for a slide projector, which system does not requiremajor changesor alterations to the associated slide projector.

Still another object of the present invention is the provision of arandom selection system of the type described, which system includes acontrol box remote from the projector and including means for selectingany one of the slide-receiving spaces in the slide tray as well asincluding means for advancing or reversing the slide tray oneslide-receiving space at a time.

These and other objects and advantages of the invention will becomeapparent from the following specification disclosing a preferredembodiment shown in the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is perspective view of the componentsconstituting the random selection system according to the presentinvention showing the same associated with a slide projector;

FIG. 2 is an enlarged view of the remote control unit with the housingthereof removed for purposes of illustrating the interior components;

FIG. 3 is a view similar to FIG. 2 showing the remote unit with theinitiate button" removed and also showing an indicator masking plate ina position different from that shown in FIG. 2;

FIG. 4 is a section taken generally along the line 4-4 of FIG. 3 withcertain parts being removed;

FIG. 5 is a top plan view of a rotatable selector disk having two dialscales, one for a l-slide" tray and the other for an 80-slide" tray;

FIG. 6 is a perspective view of the other side of the disk shown in FIG.and primarily showing the means constituting arcuate contact strips;

FIG. 7 is a perspective view of the remote control housing with thecover thereof removed, this view primarily showing the l00-slide contactgear and the 80-slide contact gear;

FIG. 8 is a view of the l00-slide and 80-slide gear in assembledrelation;

FIG. 9 is a perspective view of the 80-slide contact gear only;

FIG. 10 is a perspective view of the 100-slide gear;

FIG. 11 is a perspective view of the other side ofthe 80-slide gear;

FIG. 12 is a perspective view of the remote control unit with thehousing and many parts removed and primarily showing a central bearingcolumn having a plurality of electrical slip rings thereon;

FIG. 13 is a fragmentary section taken along the line 13-13 of FIG. 2;

FIG. 13A (adjacent FIG. 5) is a fragmentary view taken along line13A'13A of FIG. 13;

FIG. 14 is an enlarged view of the attachment unit taken along the line14-14 of FIG. 1 showing this unit with the housing removed;

FIG. 15 is a top plan view of the attachment unit as seen in FIG. 14;

FIG. 16 is a view taken along the line 16-16 of FIG. 1 showing theattachment unit with its housing removed;

FIG. 17 is a perspective view similar to FIG. 16;

FIG. 18 is a perspective showing the bottom of the attachment unit andthe side thereof shown in FIG. 16;

FIG. 19 is a view taken along the line 19l9 of FIG. 14;

FIG. 20 is an electrical schematic of the random selection system;

FIG. 21 is an electrical schematic of the DC stepping motor and remotecommutator therefor;

FIG. 22 is a perspective view of the rotor of the DC stepping motor;

FIG, 23 is an enlarged, fragmentary, top plan view ofa 100- slide tray;

FIG. 24 is an enlarged plan view of the teeth on such tray;

FIG. 25 is a top plan view of the tray drive gear; and

FIG. 26 is an enlarged, fragmentary, top view of the teeth on an -slidetray.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIG. 1, the randomselection system according to the present invention includes a remotecontrol unit 10 and an attachment unit 12, the latter being detachablymounted on a slide projector 14. The remote control unit 10 and theattachment unit 12 are connected together by a multiconductor extensioncable 15. Preferably, at least one end of this cable is connected to amultiterminal jack (not shown) for detachable engagement with either theunit 10 or the unit 12 to facilitate storage of these units when not inuse.

The embodiment of the invention disclosed herein as been designed foruse with the slide projector disclosed in the application of Walter J.Hall, Ser. No. 684,202, filed Nov. 20, 1967, now US. Pat. No. 3,499,708.It will be apparent to those skilled in the art that the presentinvention can be readily adapted for use in association with other typesand forms of slide projectors, and therefore the present invention isnot to be limited for use only with the projector shown in theaforementioned Hall application. I

The remote control unit 10 includes a housing definedby a rectangularbase 16 and a shell-piece 17. The unit 10 includes a slide selector knob18 having an initiate button" 20 mounted centrally thereof. This unitalso includes a so-called one-slide advance button 21 and a one-slidereverse button" 22. A 80-100 selector arm 24 is mounted on this unit.The top wall of the shell 17 has an aperture therein defining a windowpreferably containing a transparent plate 25 having a reference line ormark 26 thereon.

Referring particularly to FIGS. 2, 3, 5 and 6, the remote control unit10 includes a rotatably mounted disk, generally designated 28, whichdisk has an integral hub portion 29 (which defines the knob 18) on oneface thereof, this face bearing a first dial scale 30 and an 80 dialscale 31. Mounted within the hub are two pairs of diodes 33 and 34. Alsomounted within the hub 29 is a metal bracket 35 having a pair of brusharms or contacts 35a, this bracket being secured to the disk 28, (whichis formed of dielectric material) by a fastener 36. A similar metalbracket 38 includes a pair of brush arms or contacts 38a, this bracketbeing secured to the disk 28 by a fastener 39. It will be understood thebrush arms 35a and 38a are vertically spaced from each other andtherefore electrically insulated from each other in all relativepositions. As noted in FIG. 5, the disk 28 includes a central bore Asnoted in FIG. 3, a fixed contact button 42 is mounted on a small disk43, the latter being suitably mounted within the hub 29 in verticalspaced relation with the bore 40. The disk 43 mounts a spring arm ormovable contact 44 which is normally in spaced relation with the contactbutton 42, the former being adapted to be engaged by the initiate button20 for closing the contacts 42, 44 when such button is depressed.

The other face of the disk 28 is illustrated in FIG. 6. This face mountsa first annular series ofdetents 46 defining a socalled 100-slide" wheeland a second annular series of detents 47 defining a so-called 80-slidewheel. Mounted within these formations is a first pair of arcuatecontact strips 49 and 50, adjacent ends of these strips being in spacedrelation and forming dielectric areas 51 and 52. The lower face of thedisk 28 also mounts an annular contact ring 53 and a further arcuatecontact ring 54. It will be understood that all contact rings or stripsare electrically insulated from each other.

The brush arms 35a are electrically connected with the an nular contactstrip 53 by means of the fastener 36; in like manner, the brush arms 38aare electrically connected with the arcuate contact strip 54 by means ofthe fastener 39. The diodes 34 connect annular contact member 53 witharcuate contact strips 49 and 50; the diodes 33 connect the arcuatestrip 54 with the contact strips 49 and 50. As will be explained belowin connection with the description of the electrical schematic, thearrangement of the diodes is such that contact strips 49 and 50 areprovided respectively with positive and negative DC voltage.

The disk 28 is rotatably mounted on a central post 56 (FIGS. 7 and 12),which post includes four contact rings 57, 58, 59 and 60 electricallyand physically separated by intermediate dielectric bands, It will beunderstood that when the disk 28 is mounted in place on the post 56, thecontact wipers 35a wipe or engage the ring 57 and the wipers 38a wipe orengage the ring 58.

Rotatably mounted on the post 56 just below the disk 28 is a so-calledl-slide gear 62 (FIGS. 8 and having a series of teeth 63. The gear 62includes a central, circular opening 64 defining its bearing surface.This gear also contains a generally U-shaped cutout including legs 65,66 which communicate with the opening 64. An inverted U-shaped metalcontact bracket 68 is mounted on the gear 62 (which is formed ofdielectric material) by fasteners 69, the ends of this bracket beingreceived in the cutout portions 65 and 66. The bracket 68 includes anintegral arm 70 mounting a seeking contact 71 at the end thereof. Asnoted in FIG. 8, the bracket 68 includes an integral pair of contactarms 68a.

Rotatably mounted on the post 56 below the gear 62 for rotationindependently thereof is a so-called 80-slide gear 74 having an annularseries of gear teeth 75. The gear 74 is dished out and includes anintegral, upstanding hub formation 76 which mounts a contact ring 78.The upper end of the formation 76 also mounts an arcuate contact strip79 by means of fasteners 80. Strip 79 includes an integral arm 81mounting at the outer end thereof a seeking contact 82. Mounted on thestrip 79 is another contact strip which includes a pair of contact wiperarms 79a, which arms are in wiping engagement with the ring 59 on thepost 56. It will be understood the bracket 79 and the various contactsthereon are all in insulated spaced relation from the contact ring 78.

The gear 74 includes a central bore 84 which extendsthrough the hubformation 76. The underside of the gear 74 (FIG. 11) supports a contactbracket 85 by means of a fastener 86. This bracket includes integralcontact arms or wipers 85a which wipe or engage the contact ring 60 onthe post-56. A conductor wire 87 defines an electrical connectionbetween the ring 78 and the contact bracket 85. When the gear 62 and 74are mounted on the post 56, the contact wipers 68a engage the contactring 78 thereby establishing an electrical path between the contact ring60 and the seeking contact 71. It will be readily apparent that acurrent path is established between the ring 59 and the seeking contact82.

The post 56 is suitably mounted centrally of a dished-out member 89(FIG. 12) which member is in turn supported on a plate 90. The member 89has an annular rim 89a which engages the underside of the gear 74 andthereby rotatably supports the latter. The gear 62 is rotatablysupported by engagement of its bearing surface 64 with the hub formation76 on the gear 74. I I

The plate 90 is mounted in vertical spaced relation from the base 16 bya plurality of posts 91. This plate mounts a bracket 93 which in turnmounts a gear 94 integral with a pinion gear 95. As noted in FIG. 7, thepinion gear 95 meshes with the teeth 63 and 75 on the gears 62 and 74,respectively. As will be explained more fully hereinbelow, the gear 62includes a greater number of teeth 63 than the number of teeth 75 on thegear 74. Accordingly, the pinion gear 74 which is rotated at a constantrate, will drive the gear 74 at a greater velocity or annular rate thanthe gear 62. Gear 94 meshes with a gear 96 which is mounted on theoutput shaft of a DC stepping motor 97, the latter being suitablymounted between the base 16 and the plate 90.

Turning now particularly to FIGS. 7 and 12, it will be noted that theselector switch member 24 is integral with a bar 99, the latter beingsuitably mounted on the plate 90 for reciprocal sliding movement. Thebar 99 includes a notch 100 in the underside thereof which receives theoperating member or button 101 of a two-position switch (not shown)which is of conventional construction. The end of bar 99 remote from themember 24 mounts an integral bracket 102 having an aperture 103 and ahorizontally disposed leg 104.

Referring to FIGS. 2 and 3, the aperture 103 in the bracket portion 102rockably mounts a swivel member 105, the latter being in abuttingrelation with one end of a coil spring 106. The coil spring encircles astem member 108 which is integral with a hemispherical formation 190. Itwill be understood the formation 109 and its stem 108 are movablerelative to the swivel 105, the spring 106 serving to urge these membersapart.

The hemispherical formation 109 is rockably received in an aperture 110(FIG. 4) defined in a tab integral with a detent actuator 112. Thisactuator is pivotally mounted about a pin 113, the latter being mountedfrom a block 114 which is in turn suitably supported on the plate 90.The block 114 includes bores 115 and 116 respectively mounting a pair ofdetent balls (not shown) positioned for being alternately biased intoengagement with the detent formations 46 and 47 on the disk 28. Theactuator 112 includes generally oppositely disposed arms 117 and 118having formations (not shown) on their distal ends for engagement of thedetent balls.

' The leg 104 on the bracket 102 which is integral with the bar 99pivotally mounts one end of an arm 120, the other end of this arm beingpivotally mounted to an intermediate portion of an arm 121. One end ofthe arm 121 is pivotally mounted from a post 122 (FIGS. 7 and 12)suitably supported from the plate 90. The other end of the arm 121 ispivotally connected to a masking plate 123 which is arcuate in shape andadapted alternately to mask portions of the dial scales 30 and 31. Themasking plate includes an integral leg portion 124 the distal end ofwhich is pivotally mounted to one end of an arm 125; the other end ofthis arm is pivotally mounted from a post 126. It should be apparentthat shifting movement of the bar 99, which is brought about by manualactuation of the arm 24, results in swinging the masking plate 123 backand forth between the positions shownin FIGS. 2 and 3. It should also beapparent that this shifting movement of the bar 99 will serve to rockthe detent actuator 112 for alternately detentin g the detent formations46 and 47 on the disk 28.

When the selector arm 24 is moved to the 100-s1ide position, the switchactuator 101 is positioned for establishing the appropriate circuitry(which will be explained hereinbelow), the masking plate 123 ispositioned for obscuring a portion of the 80-slide dial 31 and theactuator 112 is rocked for biasing one of the detent balls intoengagement with the detent formations 46. The detent ball will beyieldably engaged with these detent formations by the action of thespring 106. When the selector 24 is moved to the 80-slide position, theswitch actuator 101 is moved to its other position, the masking plate103 1 then obscures a portion'of the IOU-slide indicator dial 30, and

the other detent ball is yieldably urged intoengagement with the detentformations 47.

The disk 28 is preferably formed of translucent material. A diffuserplate 128 (FIGS. 2 and 3) is mounted beneath the disk 28 in alignmentwith the window 25 formed in the housing shell 17, this diffuser platebeing mounted on a post 129 in turn supported from the plate 90. A bulb130 is mounted beneath this diffuser plate, a suitable opening beingprovided in the plate 90 to accommodate the bulb. The bulb is receivedin a conventional socket 132 supported from a bar 133 extending from thelower end of the post 129. It will be apparent the bulb 130 serves toilluminate the portion of the disk 28 which is visible through thewindow 25.

Turning to FIGS. 7, 12 and 13, the advance button" 21 is of steppedcylindrical construction and is mounted for vertical reciprocal movementin a split cylindrical formation 136 supported on the plate 90. Thelower end of the button 21 is of bifurcated construction for receivingone end of an actuator plate 137, the latter having an inclined camsurface 138. The actuator plate is mounted in a slot 90a in the plate 90for horizontal reciprocal sliding movement relative thereto. It will beunderstood the button 21 includes an inclined cam surface (not shown)for complementary engagement with the cam surface 138 thereby causingthe actuator 137 to be slid inwardly of the plate 90 when the button21is depressed.

The actuator 137 has an upstanding portion 139 mounting a pair of detentfingers 140 and 141 for respective engagement with detent formations 46and 47. The actuator 137 has the inner end thereof supporting a dowel(not shown) received in one end of a spring 143 (FIG. 13). This end ofthe actuator 137 carries a sleeve 144 for confining a portion of thespring 143. As also noted in FIG. 13, the actuator 137 has a dependingportion 145 mounting a fastener 145a for actuating engagement with acontact strip 146, the latter having a plate portion 146a secured to theunderside of plate 90 by a fastener 147.

The reverse button 22 is identical with the button 21 and is associatedwith an actuator 149 identical with the actuator 137 and in oppositehand relation therewith. The actuator 149 supports detent fingers 150and 151 and for engagement with detent formations 46 and 47,respectively. This actuator carries a dowel 153 which is received in theother end of the spring 143. A depending portion 154 of the actuatormounts a fastener 154a arranged for actuating engagement with a contactstrip 155. A plate 155a integral with this contact strip is secured tothe underside of the plate 90 by a fastener 157.

It will be apparent the spring 143 acts to urge the actuators 137, 149apart for normally holding the buttons 21 and 22 in their uppermostpositions. When the button 21 is depressed, the fingers 140, 141 arebrought into engagement with respective detent formations 46 and 47 fordetenting the disk 28 through an increment determined by which of theformations 46 and 47 is being engaged by the above-mentioned detentball. When the reverse button 22 is depressed, the disk is detented inan opposite direction. When either of the buttons 21 or 22 aredepressed, the contacts 146, 155 are closed.

As noted in FIGS. 1 and 14 through 19, the attachment unit 12 includes ahousing shell enclosing framework primarily consisting of upper andlower frame plates 159 and 160, respectively, held in parallel-spacedrelation by a plurality of posts 161. This framework mounts a small,reversible-drive motor 162 which is of conventional design and includesan output shaft 163 mounting a gear 164. A gear reduction system isdefined by a gear 165 being integral with another gear 166 both mountedfor rotation about a pin 167 supported from the frame plate 159. Thegear 166 meshes with an intermediate gear 168 which is rotatably mountedon a pin 169 also supported from the frame plate 159. Gear 168 isintegral with a smaller gear 170 which meshes with a larger gear 172fixed to the upper end ofa commutator shaft 173.

It will be apparent that energization of the motor 162 will causerotation to the commutator shaft 173. Preferably, a suitable slip driveconnection (not shown) is provided to prevent damage to theaforedescribed gear train in the event of a jam anywhere in themechanism.

The commutator shaft 173 has an enlarged central portion supporting afirst contact ring defined by three separate segments 175a 175b, and1750 (FIG. 21) which are electrically insulated from each other. Thecommutator also includes three continuous contact rings 176, 177 and178; it will be understood these three rings are respectively connectedto the segments 175a through 175a by suitable connections within theinterior of the commutator shaft.

Mounted between the frame plates 159 and 160 is a pair of brush bars 180and 181 (FIGS. 14, 16 and 17). These brush bars mount a first pair ofbrushes 182, 183 in l80 oppositely disposed relation for wipingengagement with the segments 175a through 175C. The brush mounting bars180, 181 mount second, third and fourth pairs of brushes 185, 186 and187 which are in respective wiping engagement with the rings 176, 177and 178 on the commutator.

The commutator shaft 173 carries a gear 189 (FIG. 16) adjacent the lowerend thereof, this gear being in meshing engagement with a largerdiameter gear 190 mounted on a subshaft 191. Opposite ends of thissubshaft are suitably journaled in the frame plates 159, 160. The upperend of the subshaft 191 carries a gear 192 in meshing engagement with agear 193 mounted on a drive shaft 195. This drive shaft is connected tothe gear 194 by means of a spline connection (not shown) permitting theshaft 195 to be slid back and forth between upper and lower positionsand at the same time maintaining its driven relationship with the gear194.

The drive shaft 195 mounts a drive gear 196 at the lower end thereof,the teeth of this gear being adapted for meshing engagement with theteeth 197 (FIG. 1) formed around the lower periphery of a circular slidetray 198. A button 199 is mounted on the upper end of the shaft 195 toprovide a convenient means for raising and lowering this shaft to engageand disengage the drive gear 196 from the teeth 197 of the circularslide tray.

As will be explained more fully below, the slide tray 198 shown forpurposes of illustration has 100 slide-receiving spaces and an equalnumber of teeth 197. An 80-slide circular slide tray (not shown) has 80peripherially disposed teeth for engagement by the gear 196. The teethon the gear 196 and the teeth on both of the trays are configured asexplained below such that rotation of the gear 196 through an arcdefined by 360 divided by the number of teeth on this gear the slidetray 198 will be rotated through 3.6" and the 80-slide tray will berotated through 4.5.

Means are provided for locking and unlocking the gear 196, such meansincluding a pair of locking pawls 201 (FIGS. 18 and 19) which arepivotally mounted about corresponding ends thereof on a pair of pins202, the other ends of the pawls being adapted for locking engagementwith the teeth on the gear 196 as seen in FIG. 19. The pawls includefirst integral arms 203 which are apertured for receiving opposite endsof a bowed spring 204, the latter serving to urge the pawls to thelocked position. The pawls 201 include integral, second arms 205arranged to be simultaneously engaged by a tab 206 formed on one end ofa bellcrank member 208, the latter being pivoted about one of the pins202. The other end of the bell crank is pivotally engaged with one endof a push wire 290; the other end of this wire is pivotally connected toone end of a bellcrank 210 pivoted about a pin 211. The other end ofthis bellcrank is pivotally engaged with a U-shaped bracket 212 mountedon the operating member 213 ofa solenoid 214. By reference to FIGS. 18and 19, it should be apparent that when this solenoid is energized, thepawls 201 are disengaged from the teeth of gear 196 thereby permittingfree rotation thereof and that when the solenoid is deenergized thebowed spring 204 acts to snap the pawls 201 into locking engagement withthe teeth on the drive gear.

Referring to FIGS. 14 and 17, a solenoid 216 has the actuating memberthereof connected to a disk 217 for rotating the same in acounterclockwise direction as seen in FIG. 14. This disk carries a pin(not shown) which extends through a slot 219 in an actuating plate 220,the lower end of which plate is received in a slot 221 (FIG. 18) therebymounting the plate 220 for vertical reciprocal movement. The upper endof the plate 220 has a bent-over tab 222 which is apertured forreceiving a load pin 224, opposite ends of the latter being received inappropriate fittings or bushings mounted in the frame plates 159, 160thereby mounting the pin 224 for vertical reciprocal movement. A coilspring 225 encircles a portion of the pin 224; the upper end of thisspring abuts the underside of the tab 222. The other end of this springabuts a washer 226 which is suitably connected to the pin 224. It willbe understood that when the solenoid 216 is energized the disk 217 isrotated for lowering the pin 224 to the lowermost position thereof whichis illustrated in FIG. 14. When the solenoid is deenergized, a spring228 serves to return the pin 224 to its uppermost position. One end ofthis spring is connected in a suitable aperture in the frame plate 159;its other end is connected to one end of a link 229, the other end ofwhich link is connected to the pin (not shown) carried by the disk 217.

The framework within the attachment unit 12 also supports, by suitablebracket means, a transformer 230 and a pair of relays 231, 232. Thepurpose and function of these components will be explained below inconnection with the description of the electrical schematic.

Turning to FIGS. 21 and 22, the motor 97, which is of the DC steppingtype, includes permanent magnet field pieces 235, 236 of north-southpolarity, respectively, and a rotor 237 having three coil windings withthe windings 2370, 237b and 2370 connected with slip rings 238-240 asshown. These slip rings, which are mounted on the shaft of the rotor asnoted in FIG. 22, are wiped by suitable brushes 241-243 schematicallyillustrated in FIG. 21. The brushes 241-243 are connected by theconductors 244-246 to respectivepairs of brushes 185 through 187. Therings 176-178 on the commutator shaft 173 are respectively connected tocontact segments 175a, 175b and 1750 by the conductors 248-250. It willbe understood these connections are actually formed within the interiorof the commutator shaft 173. The brushes 182, 183, which engage only twoof the segments 175a through 1750 at any one time, are provided with DCcurrent through the lines 252, 253.

What has just been described is essentially a DC stepping motor with aremote commutator. The commutator, consisting of the rings 175-178 andthe brushes 182-187 constitute a transmitter and the motor partsconsisting of the pole pieces 235, 236 and the rotor 237 constit ute areceiver. The rotor 237 will step or rotate in synchronization withrotation of the commutator shaft 173 by reason of signals generated bythe transmitter, such signals being in response to rotation of the shaft173.

The brushes 182, 183, which are provided with a source of direct currentvoltage, always engage two of the commutator segments 175a through 1750.When direct current is applied to any two of the segments 17511-1750,one coil of the rotor 237 will be connected across such rings and thetwo remaining rotor coils which are in series will be connected acrossthe same two contact segments. The magnetic field established by suchenergization rotates the rotor in conformance with known magneticprinciples. In the particular arrangement illustrated in FIG. 21, thecoil 237a is energized in such a way that the magnetic flux developedhas the south pole at the top of this coil which is thereby attracted tothe permanent north pole piece 235. The other two coils 23717 and 2370are energized such that the magnetic flux developed has the northmagnetic pole at the outer extremities of these two rotor coils therebycausing them to be attracted to the south magnetic pole piece 236.Therefore, the rotor 237 is rotated to and held in the positionillustrated so long as the brushes 182, 183 engage the contact segments175a, 175b.

As the contact segments 1750 through 1750 rotate, it will be apparentthat another combination between the brushes 182, 183 and the segmentsa-175c will be formed affecting corresponding but different combinationsof energization in the rotor coils for stepping or rotating the rotor237 to a subsequent position. It will be apparent that in the embodimentshown for purposes of illustration, six possible combinations ofenergization andconsequent magnetic polarity will result during onecomplete rotation of the commutator shaft 173. In other words, for eachone-sixth of an increment of rotation of the transmitter or commutatorshaft 173, the receiver or rotor 237 will respond in one-sixth turnincrements in synchronization therewith.

The DC stepping motor with remote commutator as just described is not ofcourse to be limited to the particular form illustrated and disclosedherein. Many variations are possible. For example, the permanent magnetfield structure illustrated may have substituted therefor anelectromagnetic field of well known and conventional configuration. Thereceiver or rotor is not of course to be limited to three-poleconstruction, as it could, for example, be of five-pole construction.Also, the rotor may be a permanent magnet and the field defined by woundconstruction.

It will be apparent to those skilled in the art that the energy requiredin the receiver is not reflected as a load on the transmitter orcommutator. The total energy absorption in the transmitter-commutator isthe mechanical input required to rotate the shaft 173. It will thereforebe appreciated the receiver or rotor can be quite delicate andresponsive to very low level signal inputs. It will also be appreciatedthat the power or torque capable of being generated by the rotor 237 isa function of the physical and electrical structure together with theamount of power switched to the rotor by the transmitter-commutator.Accordingly, it will be understood that from very low input aconsiderable amount of usable work can be obtained from the receiver orrotor 237. Therefore, the DC stepping motor with remote commutatordescribed herein provides not only a device wherein one rotatableelement will follow directions from a remotely disposed rotatableelement, but also provides a device useful as a power amplifier as well.

The DC motor with remote commutator arrangement shown provides forabsolute synchronization between the transmitter and receiver so long asthe receiver is not loaded beyond its designed torque capabilities. Itwill be apparent that the rotor 237 can be rotated in either directionin response to corresponding direction of rotation of the commutatorshaft 173.

Referring to FIG. 20, the various components of the random selectionsystem of the present invention which have not been mentioned above willnow be described. The relay 231 controls three sets of switchesconsisting of movable contacts 255a, 256a, 257a and pairs of fixedcontacts 255b, 2550, 256 b, 2560, 257b, 2570. The movable contacts arebiased to the positions illustrated; when the relay 231 is energized,the movable contacts are simultaneously moved to their other positions.

The relay 232 actuates a pair of switches consisting of movable contacts258a, 259a, and associated pairs of fixed contacts 258b, 2580,259b,2590. The movable contacts of these switches are biased to the positionillustrated. Energizing of the relay 232 results in movement of themovable contacts to their other position.

The system is energized from conventional line voltage of approximately1 15 volts, this line voltage being represented by the conductors 261,262. In the embodiment according to the present invention, line voltageis obtained from a suitable plug (not shown) on the slide projector 14.The housing 158 of the attachment unit 12 is preferably provided with apair of contact prongs (not shown) which are received in a plug on theslide projector when the unit 12 is mounted thereon.

As explained fully in the aforementioned Hall application, the projectorincludes a so-called half-cycle park switch which is represented hereinby a movable contact 263a associated with a fixed pair of contacts 263b,2630. When the slide-changing mechanism in the projector 14 positions aslide in the projection gate, the half-cycle part switch is in thecondition shown in FIG. 20. When the slide-changing mechanism hasremoved a slide from the gate and returned the same to the tray but hasnot yet positioned the next slide in the gate, i.e., when theslide-changing mechanism has moved through only one half of a cycle, themovable contact 263a is forced into engagement with the fixed contact2630.

A load or actuating button is indicated at 264. As explained in the Hallapplication, operation-of this button restores a slide in the projectiongate to its space in the tray.

The line 252 providing DC voltage to the stepping motor is connectedbetween a pair of oppositely poled diodes 265 which are connected to thelow-voltage side of the transformer 230. It will be noted that the line253 is connected to a center tap on the low-voltage side of thetransformer through the switch 258.

Lines 230a, 23Gb extend from the low-voltage side of the transformer andare connected to respective slip rings 57 and 58 on the post 56. It willbe noted these two lines serve to energize the bulb 130. Another line230C extends from the center tap on the low-voltage side of thetransformer and connects to a dead contact in the remote control unit10. This dead contact may be used in conjunction with another contact toenergize an indicator bulb (not shown) during the period of time betweenselection of a slide and arrival of such slide at the projection gate.

A voltage control network for the motor 162 is provided in the form offour diodes 266 connected in a bridge formation in shunt relation withthe motor, this bridge arrangement having a diagonal connectionincluding four diodes 267. This control network is independent of linevoltage variations over a range considerably greater than the expectedvariations from line voltage. This control is required to maintainstrict synchronization between the transmitter and receiver underopposite, extreme conditions, such as the occurrence of highline voltageat a time when the slide tray is unloaded, and the occurrence of linevoltage less than usual at a time when the tray is heavily loaded. Thevoltage control system just described controls motor speed within verynarrow limits for maintaining precise synchronization under these twodiverse conditions.

The operation of the random selection system according to the presentinvention is as follows.

Assume that the circular slide tray 198 is fully loaded with slides andoperatively positioned on the slide projector 14. Assume further thatthe unit 12 is attached to the projector and that the button 199(FIG. 1) is depressed for bringing the drive gear 196 into meshingengagement with the teeth 197 on the slide tray. Preferably, the shaft195 which rotates the drive gear is provided with an extension (notshown) on its lower end for actuating the disabling switch" described inthe above-mentioned Hall application. Actuation of this disabling switchserves to interrupt the control circuit which causes rotation of thetray 198 when the random selection system is not being used.

Since the tray 198 contains 100 slide-receiving spaces, the switchactuator 24 will be in the 100-slide position serving to locate theswitch actuator 101 in the condition illustrated in FIG. 20. Assume alsothat a slide is being projected in the projection gate. Under thiscondition, the solenoids 214, 216, the relays 231, 232 and the drivemotor 162 will be deenergized. The stepping motor 97 will likewise bedeenergized and the 100-slide seeking contact 71 will be located in thedielectric area 51 between the arcuate contact strips 49 and 50. Underthese conditions, all of the various switches will be in the conditionshown in FIG. 20.

Now assume that the operator rotates the selector knob 18 in a clockwisedirection (with reference to FIG. for locating the selected slide numberon the scale 30 (FIG. 5) beneath the mark 26 (FIG. 1) on the window 25.This action causes movement of the disk 28 for placing the plus" contactstrip 49 into engagement with the seeking contact 71. Now, the initiatebutton 20 is depressed for closing the switch contacts 42. 44 therebycompleting a circuit through the relay 231 and solenoid 214.Energization of the relay 231 causes the contacts 255a, 256a, 2570 to bebrought into engagement with respective contacts 2550, 256e, 2570. Sincethe contacts 255a, 2550 are in parallel with the contacts 42, 44, therelay 231 and solenoid 214 will remain energized after release of theinitiate button 20. Energization of the solenoid 214 actuates the lockpawls 201 for unlocking or releasing the drive gear 196. It will benoted that under these conditions, the drive motor 162 will not beenergized as thesame is shunted through the contacts 259a, 259b.

Engagement of contacts 256a, 2560 results in energization of thesolenoid 216. This causes the pin 224 to be lowered thereby depressingthe load button 264 on the slide projector 14. This actuation of theload button causes the slide-changing mechanism in the projector tocommence a cycle of operation. After the slide-changing mechanism hasmoved through a half cycle thereby removing a slide from the projectiongate and returning the same to its space in the slide tray, theslidechanging mechanism is stopped by movement of the half-cycle switchcontact 263a into engagement with the fixed contact 2630. This willresult in energization of the relay 232 which causes the movablecontacts 258a, 259a to be brought into engagement with the fixedcontacts 258e, 2590. Movement of the contact 259a into engagement withthe contact 259C removes the shunt across the motor 162 thereby causingthe same to be energized to commence rotation of the slide tray. Theengagement between the contacts 258a, 2580 provides power to thestepping motor and commutator through the low-voltage side of thetransformer 230.

As the motor 162 rotates for driving the slide tray, this motor alsorotates the commutator shaft 173 which, as previously explained, acts asa transmitter sending signals to the rotor 237 in the motor 97 wherebythe latter is rotated or stepped in synchronization with rotation of theshaft 173. This results in driving of the seeking contact 71 which willbe in wiping engagement with the arcuate strip 49,

When the seeking contact 71 reaches the dielectric area 51, the circuitis opened and relay 231, solenoid 214 and the drive motor 162 areimmediately deenergized. Movement of contact 257a into engagement withcontact 257b results in a dynamic breaking influence on the motor 162 byvirtue of short-circuiting the back EMF of the motor. Mechanicalrestraint to rotation of the tray is also brought about asdeenergization of the solenoid 214 causes the locking pawls 201 to comeinto locking engagement with the drive gear 196. The various parts areof course arranged and adapted such that the selected slide-receivingspace in the tray will be precisely positioned adjacent the projectiongate when seeking contact 71 reaches dielectric area 51.

Solenoid 216 is also deenergized when the seeking contact 71 reaches thedielectric area 51 by reason of the movable contact 256a being separatedfrom the contact 256v. This allows the load button 264 on the projectorto pop up causing the slidechanging mechanism in the projector tocomplete its cycle. Completion of the cycle causes the selected slide,which was positioned adjacent the gate, to be lowered into the gate.When the slide-changing cycle is completed, the contact 263a isdisengaged from the contact 2630 thereby resulting in deenergization ofthe relay 232, this resulting in movement of the contacts 258a, 259a tothe position illustrated in FIG. 20, thereby completing a cycle ofoperation.

As mentioned above, the diodes 33, 34 cause the contact strips 49, 50 tobe provided respectively with a plus and minus polarity. This determinesthe direction of rotation of the motor 162 and consequently thedirection of rotation of the seeking contact. In the cycle of operationjust explained, it will be appreciated that if the operator had rotatedthe knob 18 in the other direction, l.e., in a counterclockwisedirection (with reference to FIG. 20), the contact strip 50 would havebeen brought into engagement with the seeking contact thereby resultingin current flow through the motor 162 in the opposite direction. It willbe appreciated that by reason of this feature the slide tray will alwaysbe rotated in a direction which will result in the minimum amount ofrotation to bring the selected slide to the projection gate. Or in otherwords, the slide tray will never be rotated in excess of 180. It will beobvious that because of this feature the random selection system of thepresent invention can accommodate so-called box-type slide trays. Thisfeature may be referred to as providing shortway home or minor arcoperation.-

It will be appreciated that when the selector switch 24 is in the80-slide position, the operation is the same as described above. In thiscase, the switch actuator 101 is positioned for disconnecting theseeking contact 71 and connecting the seeking contact 82 in the circuit.The seeking contact 82, which has a random relationship with the seekingcontact 71, is rotated at a greater angular rate as explained below.This 80- slide tray will also be rotated at a greater rate by reason ofthe construction of the teeth on the same and the teeth on the drivegear 196, as will be explained in detail below. Inother words, the drivegear 196 and the commutator shaft 173 continue to rotate at the samerate, the rotor in the stepping rotor turns at the same rate insynchronization with the commutator shaft and therefore the pinion 95 isrotated at the same rate, and the gear 74 is rotated'at a greater ratein synchronization with the 80-slide tray.

The construction for driving the circular tray 198 and another 80-slidetray atdifferent rates from the gear 196- which is always rotated at aconstant rate is shown in FIGS. 23 through 26. Referring particularly toFIGS. 23 and 24, the tray 198 is provided with 100 teeth 197. It will benoted these teeth are greater, in terms of arcuate extent, than thevalleys or notches between the teeth. The teeth 197 may be defined asbeing the result of laying out 200 teeth on the tray 198 and thenforming or cutting every other tooth to provide the I teeth as shown.

The drive gear 196 is shown in detail in FlG.,25. This gear is providedwith teeth 196a shaped for complementary engagement with the tray teeth197. when the gear 196 is rotated through one increment which in thepresent embodiment is 36, i.e., 360. divided by l0 teeth, the tray 198is moved through a one-tooth increment of 3.6 (360 divided by 100 teeth)for indexing the tray to present the successive slide-receiving spacetherein adjacent theprojection gate.

The teeth 270 of a 80'slide tray 271 are shown in FIG. 26. The outsidediameter of such teeth is the same as the outside diameter of the teeth197 on the tray 198. It will be understood there are 80 teeth 270. Inthe embodiment according to the present invention, these teeth areformed by swinging a -pitch rack tooth cutter through l8 on each side ofthe radius 2700. It will be noted this technique provides the teeth 270with curved faces 27%. It will be realized that when the gear I96 isstepped through one increment (36) the tray 271 will be rotated through4.5", i.e., 360 divided by 80 teeth. The tray 271 has this movementimparted thereto by being accelerated due to the action of the teeth196a engaging the arcuate or curved tooth surfaces 270b. In other words,there is cooperation between the surfaces 270!) and the teeth 196a inthe nature of a cam operation to accelerate movement of the tray 271such that one increment of movement of the drive gear 196 serves torotate the tray 271 for positioning a successive slide-receiving spacetherein adjacent the projection gate.

It will be understood that the teeth on the contact gears 62, 74 arefashioned in a similar manner such that these gears are driven atdifferent rates from the pinion 95 which is rotated at a constant rate.In the embodiment according to the present invention, the l00-slide gear62 is provided with 150 teeth of conventional construction, the spacesor valleys between the teeth .being of the same size and shape (butoppositely disposed) as the teeth themselves. The gear 74 has the sameoutside diameter as the gear 62. However, the gear 74 according to theembodiment shown herein is provided with 120 teeth 75. In forming theseteeth, the depth of the cut was 0.65

inches, whereas the depth of the cut for the teeth 64 was 0.045 inches.The teeth 75 and the spaces therebetween are of the same size and shape(but in oppositely disposed relation) and are of course somewhat largerthan the teeth 64 since there are fewer of the former than the latter.This gear construction results in the pinion rotating the gears 62, 74at different angular rates.

It is to be understood the present invention is not limited toaccommodating slide trays wherein one tray contains slide-receivingspaces and the other tray contains 80 slidereceiving spaces. It will beappreciated the embodiment of the invention disclosed herein can bereadily adapted to accommodate two forms of slide trays havingslide-receiving spaces differing in number from each other and beingother than 80 or 100, so long as the difference in slide-receivingspaces between the trays is not unduly large with respect to the totalnumber of spaces in the trays.

It will be understood the slide tray 198 may be stepped in eitherdirection one space at a time by actuation of the advance and reverse"buttons 21, 22. Actuation of the button 21, for example, will cause thedisk 28 to be rotated in the proper direction by reason of theengagement between the fingers 140, 141 (FIG. 14) engaging the detentformations 46, 47. This will result in the appropriate contact strips49, 50 being brought into engagement with the seeking contact which isconnected in the circuit. This actuation of the button 21 will close thecontacts 146, thereby establishing a circuit as explained above forrotating the tray a distance represented by one space therein. Actuationof the button 22 will result in the other contacts 49, 50 being broughtinto engagement with the operative seeking-contact resulting in rotationof the tray in the other direction. The detent formations aredimensioned such thatthe formations 46 and 47 engaged by a detent ballwill be detented through an arcuate increment which will result in thetray being rotated one increment defined by one slide-receiving space.The buttons 21, 22 may be successively operated for sequentiallyprojecting the slides in the tray. I

It will be observed that the drive motor 162 is shunted by both switches257, 259. Accordingly, the drive motor cannot be energized until afterenergization of both the relay 231 and the relay 232. The latter relayis not energized until the slidechanging mechanism in the slideprojector has proceeded through a half cycle for returning a slide toits space in the tray. Accordingly, this feature prevents the slide trayfrom being rotated prior to the time the slide is returned to its spacein the tray.

It will also be apparent this double-shunt arrangement for the drivemotor 162 causes the latter to be dynamically braked as soon as therelay 231 is deenergized. This causes the tray to be positively stoppedwhen the selected slide-receiving space is positioned adjacent theprojection gate. As just mentioned above, the relay 232, which controlsthe switch 259, is not deenergized until a slide is returned to theprojection gate.

When the random selection system according to the present invention isnot being used, the slide projector 14 may still be operated withoutremoving the unit 12 from the projector. The button 199 is lifted fordisengaging the drive gear 196 from the teeth 197 on the slide tray.This action also releases the disabling switch mentioned above therebyplacing the deenergized projector drive system into operation. The loadbutton 264 on the projector may be operated by actuation of a button2240 (FIG. 1) which is mounted on top of the pin 224.

As mentioned above, the present invention is not to be limited for usewith the particular slide projector disclosed in the above-mentionedHall application. However, to the extent the Hall application may berelied upon for a complete understanding of the present invention, thedisclosure in the aforementioned Hall is incorporated herein by thisreference thereto.

It will be appreciated that it is within the scope of the presentinvention to have the attachment unit 12 formed as an integral part ofan associated slide projector. In such an arrangement, the motor 162 canserve as the sole drive motor for the tray rotating the latter uponoperation of the random selection system and also rotating the tray whenthe normal tray-indexing or advance mechanism is used.

It will be understood the present invention permits the control unit tobe remotely disposed with respect to the projector and connected theretoby a cable having a minimum number of conductors. in the embodimentaccording to-the present invention, only eight conductors are containedwithin the extension cable and therefore a standard eight-conductorcable can be used. This important feature results from the nature of thestepping motor with its remote commutator which requires, in theembodiment shown, only three wires for connecting the commutator to therotor. The unique stepping motor with this remote commutator maintainsprecise synchronization between rotation of the slide tray and theseeking contacts for precisely locating any randomly selected slidespace at the slide projection gate of the projector.

lclaim:

l. A remotely operated random selection system for a slide projector ofthe type having a slide tray and motor-driven indexing means therefor,said system comprising:

a. a control unit separate and remote from said projector comprising amotor, a seeking contact driven in an arcuate path by said motor,contact means defined by two separate segments arranged in an arcuatepath for alternate engagement by said seeking contact; and manuallyoperable selection means associated with said contact means forestablishing the extent of movement of said seeking contact to effect apredetermined circuit condition;

b. a commutator mounted on said projector and having the rotatablecomponent thereof driven by said motor-driven indexing means;

c. said motor-driven indexing means including a reversible motor;

d. a cable between said control unit and said projector electricallyconnecting the motor and the commutator to cause rotation of the formerin synchronization with the rotation of the rotatable component of thelatter; and

e. circuit means connecting the seeking contact and the segments of saidcontact means with the reversible motor for establishing either forwardor reverse signals for each selected circuit condition, depending onwhich of said segments is engaged by said seeking contact to alternatelyenergize the reversible motor in forward and reverse directions. 1

2. Random slide selection means for a slide projector of the type havinga slide tray with a plurality of slide-receiving spaces therein, saidmeans comprising:

a. drive means including a drive motor for indexing the slide tray;

b. a DC stepping motor having a remote commutator, which commutatorincludes a rotary element driven by said drive means;

c. a seeking contact driven in an arcuate path by the rotor of saidstepping motor; 7

d. nonconductive support means mounting an arcuate contact striparranged to be wiped by said seeking contact and defining a dielectricarea adjacent one end of said strip;

e. control means for selecting a number corresponding to the selectedspace in the tray, including means for positioning said contact stripwith respect to said seeking contact to establish an initial spatialrelationship between the former and the latter; and circuit meansincluding the drive motor, the seeking contact and the contact strip forestablishing a first contact condition when said seeking contact wipessaid strip and a second circuit condition when said seeking contactreaches said dielectric area, said first circuit condition causing thedrive motor to be energized and said second circuit condition causingthe drive motor to be deenergized.

3. The random slide selection means according to claim 2 further definedby:

a. another arcuate contact strip on said support means and having oneend thereof adjacent said dielectric area and adapted to be wiped bysaid seeking contact alternately with said first-mentioned contactstrip;

b. said circuit means including rectifying means providing said firststrip with positive and said another strip with negative DC voltage;

c. said drive motor being of the reversible type; and

d. said circuit means also including said another strip for alternatelyenergizing said drive motor in forward and reverse directions dependingon whether said first strip or said second strip is being wiped by saidseeking contact.

4. The random slide selection means according to claim 2 further definedby:

a. another seeking contact arranged for wiping engagement with saidcontact strip;

b. means for driving said another seeking contact from said rotor at adifferent angular rate from the rate of angular movement of thefirst-mentioned seeking contact; and

. selector means for alternately placing said seeking contacts in saidcircuit means whereby said random slide selection means may accommodateanother slide tray having a number of slide-receiving spaces differentfrom the number of slide-receiving spaces in the first mentioned tray.

5. In a slide projector of the type having a projection gate and a slidetray including a plurality of slide-receiving spaces, a system forpresenting at said gate any one of said spaces selected at randomcomprising:

a. a drive motor and means driven thereby for alternately indexing thetray in forward and reverse directions;

b. a commutator-transmitter including a rotatable element and means formechanically rotating the latter by said drive motor in synchronizationwith the indexing movement ofsaid tray;

c. motor means remotely associated with said commutatortransmitter andincluding a rotor which is rotated in synchronization with saidrotatable element in response to signals generated by thecommutator-transmitter as a result of rotation of the rotatable element;

d. a seeking contact and means connecting the same with said rotor forbeing driven in an arcuate path thereby;

e. selector contact means having support means mounting first and secondcontact strips with adjacent ends thereof in spaced relation anddefining a dielectric area therebetween, said contact strips beingarranged in an arcuate path for wiping engagement by said seekingcontact;

. slide selection means associated with said selector contact means andoperable to establish the extent of movement of said seeking contactwhich is necessary to effect a first contact condition, a second contactcondition being effected during movement of said seeking contact; and

g. circuit means connected to said drive motor, said seeking contact andsaid selector contact means and adapted to cause deenergization andenergization of said drive motor upon the occurrence of said first andsecond contact conditions, respectively, said circuit means includingrectifying means providing said first and second strips with positiveand negative DC voltage, respectively, during the occurrence of thesecond contact condition to alternately rotate the drive motor inforward and reverse directions depending on whether said first or secondstrip is being wiped by said seeking contact.

6. In a slide projector of the type having a projection gate and a slidetray with a plurality of slide-receiving spaces therein, a system forpresenting at said gate any one of said spaces selected at randomcomprising:

a. a drive motor and means driven thereby for alternately indexing thetray in forward or reverse directions;

b. a three-bar commutator-transmitter including a rotatable element;

0. means mechanically connecting said rotatable element with said drive'motor for rotating the former in synchronization with theindexingmovement of said tray;

d. a multiconductor extension cable including three conductors connectedto said commutator-transmitter;

e. a random selection control unit 'remote from said projector andincluding:

1. motor means connected to said three conductors and including a rotoradapted to be rotated in synchronization with said rotatable element inresponse to signals generated by the commutator-transmitter as a resultof rotation of the rotatable element,

. a seeking contact and means connecting the same with said rotor forbeing driven in an arcuate path thereby,

. selector means having support means mounting first and second contactstrips with adjacent ends thereof in space relation and defining adielectric area therebetween, said contact strips being arranged in anarcuate path for wiping engagement by said seeking contact,

4. slide selection means associated with said selector contact means andoperable to establish the extent of movement of said seeking contactwhich is necessary to effect a first contact condition when said seekingcontact engages the dielectric area, a second contact condition beingeffected during movement of said seeking contact; and

f. circuit means connecting said drive motor, said seeking contact andsaid selector contact means via an extension cable and adapted to causedeenergization and energization of said drive motor upon occurrence ofsaid first and second contact conditions respectively, said circuitmeans including rectifying means providing said first and second contactstrips with positive and negative DC voltage, respectively, during theoccurrence of the second contact condition to alternately rotatethedrive motor in forward and reverse directions depending on whether saidfirst or second strip is being wiped by said seeking contact.

7. The system according 'to claim 6, wherein the total is engaged b saidseeking contact, the motor being deenerglzed y arrival of the seekingcontact at sai dielectric area; and g. manually operated selection meansincluding indicator means for rotating said disk in either direction forbringing one of said strips into engagement with said seeking contactfor establishing an initial spatial relationship between the latter andsaid dielectric area. 9. The system according to claim 8 further definedby:

. said circuit means including a random selection initiate switch" and asingle-slide initiate switch," which switches are connected in paralleland are of the normally open type;

b. a manually operated one-slide advance actuator" and a manuallyoperated one-slide reverse actuator";

. mechanism connecting each of said actuators with said single-slideinitiate switch for closing the latter upon actuation of either of saidactuators; and

d. stepping means adapted to engage said disk and operated by each ofsaid actuators for stepping said disk in advance and reverse directionsin response to actuation of said advance actuator and said reverseactuator, respectively.

10. The system according to claim 8 further defined by:

a. a second seeking contact mounted for being driven by said rotor in anarcuate path for alternate wiping engagement with said contact strips atan angular rate of movement different from the rate of movement of saidfirstmentioned seeking contact; and

b. selector switch means for alternately placing said first and secondseeking contacts in said circuit means thereby adapting said projectorto accommodate another tray having a number of slide-receiving spacesdifferent from the number of slide-receiving spaces in saidfirst-mentioned tray.

11. The system according to claim 10 further defined by:

a. said indicator means including first and second numerical indiciameans corresponding respectively to the number of slide-receiving spacesin said first'mentioned tray and said second-mentioned tray;

b. operating means for said selector switch means; and

c. masking means shiftably mounted for alternately obsecuring at least aportion of saidfirst and second indicia number of conductors in saidextension cable is not in excess of eight,

8. in a slide projector of the type having a projection gate and. aslide tray with a plurality of slide-receiving spaces therein, a systemfor presenting at said gate any one of said spaces selected at randomcomprising:

and a slide tray with a plurality of slide-receiving spaces, a systemfor presenting at said gate any one of said spaces a. drive meansincluding a reversible drive motor for alternately indexing the tray inadvance and reverse directions;

and means mechanically rotating the same by said drive motor insynchronization with indexing movement of said tray;

. receiving means remote from said commutator'transmitter and includingmotor means having a rotor associated with said commutator-transmitterwherein the rotor is rotated in synchronization with said element inresponse to signals generated by the commutator-transmitter as theresult of rotation of the rotatable element;

d. a rotatably mounted disk having first and second arcuate contactstrips thereon with ends of the strips being in spaced relation andadjacent a dielectric area;

e. a seeking contact mounted for being driven by said rotor in anarcuate path for alternate wiping engagement with said strips;

f. circuit means connecting said reversible drive motor, said strips andsaid seeking contact, which circuit means includes rectifying meansproviding said first and second strips with positive and negative DCvoltage, respectively, the circuit means being adapted alternately toenergize said drive motor in forward and reverse directions asdetermined by whether said first strip or said second strip selected atrandom comprising:

a. indexing means including a reversible electric motor and an indexingmember driven thereby, which number is engageable with a slide tray forindexing the latter in forward and reverse directions in response toforward and reverse directions in response to forward and reverseenergization of said motor, respectively;

b. circuit means connected with said motor and including selector meansfor one-at-a-time selection of numbers corresponding to the spaces inthe associated slide tray;

0. said selector means including relatively movable contacts forestablishing a discreet spatial relationship of such contacts for eachnumber selected by the selector means and for establishing forward orreverse signals for each of said contact relationships to alternatelyenergize said motor in forward and reverse directions which results inthe minimum amount of movement of said indexing member 6 5 to presentthe selected tray space at said gate.

13. The system according to claim 12 wherein said relatively movablecontacts include a pair of arcuate contacts movable in response tooperation of said selection means and a seeking contact driven insynchronization with said indexing means and arranged for one-at-a-timewiping engagement of said arcuate contacts, said circuit means providingsaid arcuate contacts with respective plus and minus polarity.

1. A remotely operated random selection system for a slide projector ofthe type having a slide tray and motor-driven indexing means therefor,said system comprising: a. a control unit separate and remote from saidprojector comprising a motor, a seeking contact driven in an arcuatepath by said motor, contact means defined by two separate segmentsarranged in an arcuate path for alternate engagement by said seekingcontact, and manually operable selection means associated with saidcontact means for establishing the extent of movement of said seekingcontact to effect a predetermined circuit condition; b. a commutatormounted on said projector and having the rotatable component thereofdriven by said motor-driven indexing means; c. said motor-drivenindexing means including a reversible motor; d. a cable between saidcontrol unit and said projector electrically connecting the motor andthe commutator to cause rotation of the former in synchronization withthe rotation of the rotatable component of the latter; and e. circuitmeans connecting the seeking contact and the segments of said contactmeans with the reversible motor for establishing either forward orreverse signals for each selected circuit condition, depending on whichof said segments is engaged by said seeking contact to alternatelyenergize the reversible motor in forward and reverse directions. 2.Random slide selection means for a slide projector of the type having aslide tray with a plurality of slide-receiving spaces therein, saidmeans comprising: a. drive means including a drive motor for indexingthe slide tray; b. a DC stepping motor having a remote commutator, whichcommutator includes a rotary element driven by said drive means; c. aseeking contact driven in an arcuate path by the rotor of said steppingmotor; d. nonconductive support means mounting an arcuate contact striparranged to be wiped by said seeking contact and defining a dielectricarea adjacent one end of said strip; e. control means for selecting anumber corresponding to the selected space in the tray, including meansfor positioning said contact strip with respect to said seeking contactto establish an initial spatial relationship between the former and thelatter; and f. circuit means including the drive motor, the seekingcontact and the contact strip for establishing a first contact conditionwhen said seeking contact wipes said strip and a second circuitcondition when said seeking contact reaches said dielectric area, saidfirst circuit condition causing the drive motor to be energized and saidsecond circuit condition causing the drive motor to be deenergized.
 2. aseeking contact and means connecting the same with said rotor for beingdriven in an arcuate path thereby,
 3. selector means having supportmeans mounting first and second contact strips with adjacent endsthereof in space relation and defining a dielectric area therebetween,said contact strips being arranged in an arcuate path for wipingengagement by said seeking contact,
 3. The random slide selection meansaccording to claim 2 further defined by: a. another arcuate contactstrip on said support means and having one end thereof adjacent saiddielectric area and adapted to be wiped by said seeking contactalternately with said first-mentioned contact strip; b. said circuitmeans including rectifying means providing said first strip withpositive and said another strip with negative DC voltage; c. said drivemotor being of the reversible type; and d. said circuit means alsoincluding said another strip for alternately energizing said drive motorin forward and reverse directions depending on whether said first stripor said second strip is being wiped by said seeking contact.
 4. Therandom slide selection means according to claim 2 further defined by: a.another seeking contact arranged for wiping engagement with said contactstrip; b. means for driving said another seeking contact from said rotorat a different angular rate from the rate of angular movement of thefirst-mentioned seeking contact; and c. selector means for alternatelyplacing said seeking contacts in said circuit means whereby said randomslide selection means may accommodate another slide tray having a numberof slide-receiving spaces different from the number of slide-receivingspaces in the first mentioned tray.
 4. slide selection means associatedwith said selector contact means and operable to establish the extent ofmovement of said seeking contact which is necessary to effect a firstcontact condition when said seeking contact engages the dielectric area,a second contact condition being effected during movement of saidseeking contact; and f. circuit means connecting said drive motor, saidseeking contact and said selector contact means via an extension cableand adapted to cause deenergization and energization of said drive motorupon occurrence of said first and second contact conditionsrespectively, said circuit means including rectifying means providingsaid first and second contact strips with positive and negative DCvoltage, respectively, during the occurrence of the second contactcondition to alternately rotate the drive motor in forward and reversedirections depending on whether said first or second strip is beingwiped by said seeking contact.
 5. In a slide projector of the typehaving a projection gate and a slide tray including a plurality ofslide-receiving spaces, a system for presenting at said gate any one ofsaid spaces selected at random comprising: a. a drive motor and meansdriven thereby for alternately indexing the tray in forward and reversedirections; b. a commutator-transmitter including a rotatable elementand means for mechanically rotating the latter by said drive motor insynchronization with the indexing movement of said tray; c. motor meansremotely associated with said commutator-transmitter and including arotor which is rotated in synchronization with said rotatable element inresponse to signals generated by the commutator-transmitter as a resultof rotation of the rotatable element; d. a seeking contact and meansconnecting the same with said rotor for being driven in an arcuate paththereby; e. selector contact means having support means mounting firstand second contact strips with adjacent ends thereof in spaced relationand defining a dielectric area therebetween, said contact strips beingarranged in an arcuate path for wiping engagement by said seekingcontact; f. slide selection means associated with said selector contactmeans and operable to establish the extent of movement of said seekingcontact which is necessary to effect a first contact condition, a secondcontact condition being effected during movement of said seekingcontact; and g. circuit means connected to said drive motor, saidseeking contact and said selector contact means and adapted to causedeenergization and energization of said drive motor upon the occurrenceof said first and second contact conditions, respectively, said circuitmeans including rectifying means providing said first and second stripswith positive and negative DC voltage, respectively, during theoccurrence of the second contact condition to alternately rotate thedrive motor in forward and reverse directions depending on whether saidfirst or second strip is being wiped by said seeking contact.
 6. In aslide projector of the type having a projection gate and a slide traywith a plurality of slide-receiving spaces therein, a system forpresenting at said gate any one of said spaces selected at randomcomprising: a. a drive motor and means driven thereby for alternatelyindexing the tray in forward or reverse directions; b. a three-barcommutator-transmitter including a rotatable element; c. meansmechanically connecting said rotatable element with said drive motor forrotating the former in synchronization with the indexing movement ofsaid tray; d. a multiconductor extension cable including threeconductors connected to said commutator-transmitter; e. a randomselection control unit remote from said projector and including:
 7. Thesystem according to claim 6, wherein the total number of conductors insaid extension cable is not in excess of eight.
 8. In a slide projectorof the type having a projection gate and a slide tray with a pluralityof slide-receiving spaces therein, a system for presenting at said gateany one of said spaces selected at random comprising: a. drive meansincluding a reversible drive motor for alternately indexing the tray inadvance and reverse directions; b. a commutator-transmitter including arotatable element and means mechanically rotating the same by said drivemotor in synchronization with indexing movement of said tray; c.receiving means remote from said commutator-transmitter and includingmotor means having a rotor associated with said commutator-transmitterwherein the rotor is rotated in synchronization with said element inresponse to signals generated by the commutator-transmitter as theresult of rotation of the rotatable element; d. a rotatably mounted diskhaving first and second arcuate contact strips thereon with ends of thestrips being in spaced relation and adjacent a dielectric area; e. aseeking contact mounted for being driven by said rotor in an arcuatepath for alternate wiping engagement with said strips; f. circuit meansconnecting said reversible drive motor, said strips and said seekingcontact, which circuit means includes rectifying means providing saidfirst and second strips with positive and negative DC voltage,respectively, the circuit means being adapted alternately to energizesaid drive motor in forward and reverse directions as determined bywhether said first strip or said second strip is engaged by said seekingcontact, the motor Being deenergized by arrival of the seeking contactat said dielectric area; and g. manually operated selection meansincluding indicator means for rotating said disk in either direction forbringing one of said strips into engagement with said seeking contactfor establishing an initial spatial relationship between the latter andsaid dielectric area.
 9. The system according to claim 8 further definedby: a. said circuit means including a ''''random selection initiateswitch'''' and a ''''single-slide initiate switch,'''' which switchesare connected in parallel and are of the normally open type; b. amanually operated ''''one-slide advance actuator'''' and a manuallyoperated ''''one-slide reverse actuator''''; c. mechanism connectingeach of said actuators with said single-slide initiate switch forclosing the latter upon actuation of either of said actuators; and d.stepping means adapted to engage said disk and operated by each of saidactuators for stepping said disk in advance and reverse directions inresponse to actuation of said advance actuator and said reverseactuator, respectively.
 10. The system according to claim 8 furtherdefined by: a. a second seeking contact mounted for being driven by saidrotor in an arcuate path for alternate wiping engagement with saidcontact strips at an angular rate of movement different from the rate ofmovement of said first-mentioned seeking contact; and b. selector switchmeans for alternately placing said first and second seeking contacts insaid circuit means thereby adapting said projector to accommodateanother tray having a number of slide-receiving spaces different fromthe number of slide-receiving spaces in said first-mentioned tray. 11.The system according to claim 10 further defined by: a. said indicatormeans including first and second numerical indicia means correspondingrespectively to the number of slide-receiving spaces in saidfirst-mentioned tray and said second-mentioned tray; b. operating meansfor said selector switch means; and c. masking means shiftably mountedfor alternately obsecuring at least a portion of said first and secondindicia means, said masking means being shifted in response to operationof said operating means.
 12. In a slide projector of the type having aprojection gate and a slide tray with a plurality of slide-receivingspaces, a system for presenting at said gate any one of said spacesselected at random comprising: a. indexing means including a reversibleelectric motor and an indexing member driven thereby, which number isengageable with a slide tray for indexing the latter in forward andreverse directions in response to forward and reverse directions inresponse to forward and reverse energization of said motor,respectively; b. circuit means connected with said motor and includingselector means for one-at-a-time selection of numbers corresponding tothe spaces in the associated slide tray; c. said selector meansincluding relatively movable contacts for establishing a discreetspatial relationship of such contacts for each number selected by theselector means and for establishing forward or reverse signals for eachof said contact relationships to alternately energize said motor inforward and reverse directions which results in the minimum amount ofmovement of said indexing member to present the selected tray space atsaid gate.
 13. The system according to claim 12 wherein said relativelymovable contacts include a pair of arcuate contacts movable in responseto operation of said selection means and a seeking contact driven insynchronization with said indexing means and arranged for one-at-a-timewiping engagement of said arcuate contacts, said circuit means providingsaid arcuate contacts with respective plus and minus polarity.